This invention concerns apparatus and methods for providing dimensionally stable absorbent bodies which comprise cellulose fibers and, in particular, concerns providing such bodies compressed into cylindrical tampons having a rounded or domed tip. Specifically, this invention provides methods and apparatus for manufacturing dimensionally stabilized tampons with a domed tip having a smooth surface.
Absorbent, cylindrical tampons are now widely used for a number of absorbent purposes in the medical and dental field but are primarily used in the field of feminine hygiene as catamenial tampons. In this latter field, there are two basic types: digitally inserted tampons, inserted with the fingers, and applicator tampons inserted with the aid of an applicator. Both types are usually made by folding or rolling a loosely associated, generally rectangular strip of absorbent material, usually fibrous and cellulosic in nature, into a blank and then compressing the blank into a cylindrically shaped product. In the case of digital tampons, the product is then wrapped and packaged and, in the case applicator tampons, the product is first inserted into the applicator and then wrapped and packaged.
In both instances it is highly desirable that the tampon maintains its final compressed shape and presents a smooth outer surface at the dome whereby both the removal from the applicator and/or packaging and the insertion into the vagina are facilitated. To this end, the art has provided various suggestions for attaining shape stability and surface smoothness of the dome tip. In U.S. Pat. No. 4,081,884 for example, it has been suggested that a tampon blank be first radially compressed and then axially compressed and, while in the axially compressed state, heated to impart a set to the compressed body. The axial compression is applied to the extent that the axially compressed tampon is about 90 to about 98% of the desired length of the tampon in its final state. Owing to the heat setting technique described therein, the tampon is said to "grow" only moderately i.e. 2-10%, based on the final length. While this technique does indeed produce a relatively dimensionally stable tampon, unfortunately the required heating step entails expensive equipment and is particularly difficult to carry out at the high production speeds (of up to fifteen hundred tampons per minute) required for practical commercialization.
The art has also made suggestions with respect to presenting a smooth forward or insertion end for the tampon and, in particular for presenting a tapered, domed, or hemispherical end for a tampon to facilitate insertion. Such a suggestion may be found in U.S. Pat. No. 3,738,364 wherein a ram having a recess designed to impart a tapered shaped to a tampon blank is described. Most recently, in European Patent Application 94/102244.4 filed on Feb. 14, 1994, there is described a tampon blank which is axially compressed in a cylinder between two rams with the insertion end ram having a cup like recess to impart a hemispherical shape to the insertion end of a tampon. Such a system is found to work well for a moderate degree of axial compression. On the other hand, as will be described in greater detail herein drawbacks are inherent in such systems. This is particularly true in seeking to obtain dimensional stability without resorting to a heat setting step and at the same time attempting to dome the insertion end of the tampon.